A Minimum Equipment List (MEL) deferral allows an aircraft to continue operating with certain equipment inoperative, subject to specific conditions and time limits. PlaneConnection tracks MEL deferrals as part of the discrepancy management system, linking them to aircraft records, dispatch decisions, and maintenance workflows.
MEL Deferral Statuses
Each discrepancy record that involves an MEL deferral carries its own status tracking the resolution lifecycle.
| Status | API Value | Dispatch Impact | Description |
|---|
| Open | open | Evaluated per flight | Discrepancy has been reported but no deferral decision has been made. The item must be evaluated before each flight. |
| Deferred | deferred | Conditionally dispatchable | Item has been deferred under the MEL with a specific category and time limit. Aircraft may dispatch subject to MEL conditions. |
| In Progress | in_progress | Depends on work scope | Corrective action is underway. The aircraft may or may not be available depending on the nature of the repair. |
| Resolved | resolved | No impact | Item has been repaired, tested, and returned to service. No further dispatch restrictions. |
Deferral Lifecycle
MEL Categories
The FAA defines four MEL deferral categories (A through D), each with a specific repair interval. PlaneConnection tracks the category to calculate the deferral expiration date and trigger alerts.
| Category | Repair Interval | Description |
|---|
| A | As specified in MEL | Items that must be repaired within the time frame specified in the MEL entry. Typically the most time-critical deferrals. |
| B | 3 consecutive calendar days | Items that must be repaired within 3 calendar days (excluding the day of discovery). |
| C | 10 consecutive calendar days | Items that must be repaired within 10 calendar days (excluding the day of discovery). |
| D | 120 consecutive calendar days | Items that must be repaired within 120 calendar days (excluding the day of discovery). Least urgent deferrals. |
Deferral intervals are measured in consecutive calendar days, not flight days or business days.
The day the discrepancy is discovered does not count toward the interval. If a Category B item is
deferred on Monday, it must be repaired by end of day Thursday.
Regulatory Basis
MEL deferrals are governed by several Federal Aviation Regulations:
| Regulation | Requirement |
|---|
| 14 CFR 91.213 | Establishes when an aircraft may be operated with inoperative instruments and equipment. References the operator’s approved MEL. |
| 14 CFR 135.179 | Requires Part 135 operators to have an approved MEL. Specifies that the MEL must be based on the Master MEL (MMEL) for the aircraft type. |
| 14 CFR 91.403 | Owner/operator responsibility for maintaining the aircraft in airworthy condition. |
| MMEL / MEL Policy Letter 25 | FAA guidance on MEL revision and amendment procedures. |
PlaneConnection does not replace the operator’s approved MEL document. The system tracks
deferral records and expiration dates to support dispatch decisions. Always refer to the approved
MEL for specific deferral conditions, placards, and operating procedures (O) and maintenance (M)
procedures.
Discrepancy Record Fields
Each MEL deferral is tracked as a discrepancy record with additional MEL-specific fields:
| Field | Type | Required | Description |
|---|
title | String | Yes | Short description of the discrepancy (e.g., “Left cabin door seal leaking”). |
ata_chapter | String | No | ATA 100 chapter code (e.g., “52 — Doors”). |
description | Text | Yes | Detailed description of the discrepancy. |
severity | Enum | Yes | Severity level: minor, major, critical, grounding. |
status | Enum | Auto | Current lifecycle status: open, deferred, in_progress, resolved. |
mel_category | Enum | Conditional | MEL category (A, B, C, or D). Required when status is deferred. |
mel_certificate_number | String | No | MEL certificate or reference number for the deferral. |
deferred_date | Date | Conditional | Date the item was deferred. Required when status is deferred. |
ground_aircraft | Boolean | No | Whether this discrepancy grounds the aircraft (prevents dispatch). |
resolution | Text | Conditional | Description of the corrective action taken. Required when status is resolved. |
resolved_by | String | Conditional | Person who performed the repair. Required when status is resolved. |
resolved_date | Date | Conditional | Date the item was resolved. Required when status is resolved. |
work_order_ref | String | No | Reference to an external work order or maintenance tracking number. |
Severity Levels
| Severity | Description | Dispatch Impact |
|---|
| Minor | Cosmetic or convenience item. Does not affect airworthiness. | Dispatch normally with notation. |
| Major | Affects aircraft capability but can be deferred under MEL. | Dispatch with MEL conditions applied. |
| Critical | Significant impact on aircraft systems. May require operational limitations. | Dispatch only with chief pilot or DO approval. |
| Grounding | Aircraft is not airworthy. Cannot be deferred. | Aircraft grounded until resolved. |
Corrective Actions
Each discrepancy can have multiple corrective action records tracking the resolution steps:
| Field | Type | Description |
|---|
description | Text | Description of the corrective action step. |
assigned_to | String | Person or vendor assigned to perform the action. |
status | Enum | Action status: pending, in_progress, completed. |
completed_at | Timestamp | When the corrective action was completed. |
completed_by | String | Person who completed the action. |
Manage MEL Deferrals
Step-by-step guide to creating and resolving MEL deferrals.
Aircraft Statuses
How aircraft status interacts with deferral dispatch decisions.
Manage Discrepancies
General discrepancy tracking and squawk management.
Track Due Items
Maintenance due-item tracking and scheduling.
